During the previous weeks I saw a lot of posts and articles that confirmed the fact that Google uses machine learning into the spam algorithms already. This was confirmed on Twitter by Murat Yatagan who is a former Google spam fighter. He worked on search quality and spam for several years and was focused on the Turkish market. He has confirmed that machine learning is being used in some ways in the spam algorithm. His exact first words after the question were:

You think, machine learning was not in the game already.

Barry Schwartz did want this to be confirmed and asked again, to which Murat Yatagan replied positively. At the moment Murat is doing SEO which is not unnatural for former spam fighters at Google. From this information we can make the conclusion that Google are always trying to progress constantly.